1. Field of the Invention
This invention relates to a liquid jet recording head by which liquid is jetted to form flying liquid droplets for recording.
2. Description of the Prior Art
Ink jet recording methods (liquid jet recording methods) have recently drawn public attention because noise caused by recording is negligibly small, high speed recording is possible and recording can be effected on plain paper without any special treatment such as fixation.
Among them, liquid jet recording methods disclosed in Japanese Patent Application Laid-open No. 51837/1979, German Laid-open (DOLS) No. 2843064, U.S. Pat. No. 4,330,787 and U.S. Pat. No. 4,490,728 are different from other liquid jet recording methods in that thermal energy is applied to liquid to produce a driving power for discharging liquid droplets.
That is, according to the recording methods disclosed in the above-mentioned references, the liquid is subjected to heat energy which changes its state by abruptly increasing its volume. The resulting force due to the state change jets the liquid through an orifice at the tip of the recording head portion to form flying droplets which attach to a receiving member to effect recording.
In particular, the liquid jet recording method disclosed in the DOLS 2843064 can be very effectively applied in a so-called "drop-on demand" recording method and further more, can be easily used for recording heads of a full line type and a high density multi-orifice type. Thus, images of high resolution and high quality can be obtained at a high speed.
An on-demand type recording method refers to a recording method in which, upon forming recording images, droplets necessary for forming images are discharged in response to input signals. According to this method, there is no necessity of recovering and recirculating the ink. A continuous type recording method, where ink droplets are continuously discharged, (some ink droplets are used for recording and some are not, dependening on the images to be recorded) needs such recovery and recirculation of ink. Therefore, the on-demand type rcording apparatus is more suitable for miniaturizing and simplifying the apparatus than the continuous type recording. The full line type method refers to a method wherein orifices are arranged along the full recording width of a record receiving (member such as paper), and therefore, the full line type need not scan in the direction of paper width by the recording head. Thus, the full line type is suitable for increasing the recording speed as well as miniaturizing and simplifying the apparatus. In the full line type recording apparatus, for example, in the case of recording the full width of A-4 size paper (210 mm) with 8 orifices per 1 mm, 1680 orifices are continuously arranged resulting in a high density multi-orifice apparatus.
The recording head portions of an apparatus used in the above-mentioned recording method comprises a liquid discharging portion constituted of orifices and liquid flow paths communicating with the orifices and having heat actuating portions applying thermal energy for discharging liquid droplets to liquid, and electrothermal transducers for generating thermal energy.
Such a recording head may be constituted of a plurality of orifices arranged in line. Liquid flow paths communicating with respective orifices communicate with a common liquid chamber, and liquid may be fed to the liquid chamber from a liquid tank.
According to conventional color recording methods, that is, recording two or more colors, recording heads corresponding to each color are, in general, arranged depending upon the necessary number of colors, and ink is fed to the respective heads from an ink tank.
That is, in the case of recording two colors, e.g. red and black, there is used a recording head for red ink and a recording head for black ink. In the case of recording four or more colors, at least one recording head for each color, e.g. yellow, magenta, cyan and black is usually used. Color recording according to such a method has an advantage in that it is sufficient to only arrange recording heads of the same structure corresponding to the number of the necessary color. However, upon arranging two or more recording heads, high accuracy is required with respect to the relative positions of the recording heads. In order to meet such requisite, highly accurate processing is disadvantageously required for fabricating the recording heads and fixing devices for the recording heads.
The demand for recording color images of high resolution and high quality has been recently increasing to a great extent. The above-mentioned methods, where a plurality of recording heads are arranged, can not sufficiently satisfy the demand. High accuracy as to the position of recording dot on a receiving paper is required so that a particular processing of the recording head and fixing device should be contrived. As a result, the manufacturing cost becomes inevitably very high. Further, it is not easy to exchange the recording head since a severe adjustment of position is necessary.
In addition, when recording heads corresponding to the number of colors are so arranged, as the number of colors increases, the total volume of the recording head becomes so large that the recording head is difficult to apply to a small and compact printer. In addition, the total weight of the head increases. As a result, the running system of a carriage carrying such a head for recording is disadvantageously heavily loaded.